UK doctors subject to complaints procedures are at risk of becoming depressed and suicidal, according to research.

Those referred to the General Medical Council (GMC), seem to be most at risk of mental ill health, the research published in the online journal BMJ Open found.

7926 doctors completed a questionnaire which was included in the final analysis which found that 49% of them had faced a complaint in the past.

The respondents were streamed into three groups: those subject to a current or ongoing complaint within the past six months, those who had endured a complaint more than six months ago, and those who had no personal experience of a complaint.

The survey questions were designed to probe attitudes to any type of complaints procedure, ranging from informal through to referral to the GMC, as well as the psychological and professional fall-out of going through the process, and what might be done to improve it.

Around one in five respondents (22.5%) had no personal experience of a complaint, almost half (49%) had faced a complaint in the past, and more than one in four (28.5%) had done so recently.

Just under 17% of those with a recent complaint were moderately to severely depressed, and they were 77% more likely to report these symptoms than doctors in the other two groups, after taking account of influential factors.

And they were twice as likely as those who had no personal experience of a complaint to harbour thoughts of self-harm or suicide.

A similar proportion (15%) of those in the recent/ongoing complaints category were also twice as likely to have clinically significant levels of anxiety as doctors with no personal experience of a complaint.

Levels of psychological distress paralleled the type of complaint. Doctors who had been referred to the GMC reported the highest levels of depression (more than 26%), anxiety (more than 22%), and thoughts of self-harm (more than 15%).

Doctors subject to a recent or ongoing complaint were also more likely to have poorer health and wellbeing, including gut problems, insomnia, and relationship issues.

Meanwhile, 80% of those who had experienced a complaint said they had changed their clinical practice as a direct result, deploying tactics such as avoidance, not carrying out difficult surgery, for example, or hedging, ordering too many investigations, and in some cases, acting against their professional judgment.

Furthermore, almost three out of four of those who had not been the subject of a complaint said they had also changed their clinical practice after witnessing a colleague's experience of going through the process.

"These behaviours are not in the interest of patients and may cause harm, while they may also potentially increase the cost of healthcare provision," the researchers said.

They added that the overall response rate (7,926 doctors fully completed the survey, out of an online survey of more than 95,000 UK doctors in 2012) may mean that these findings are not truly representative of doctors working in the UK, and this is an observational study so no definitive conclusions about cause and effect can be drawn.

The researchers added: "However, a system that is associated with high levels of psychological morbidity among those going through it is not appropriate. Most importantly, a system that leads to so many doctors practising defensive medicine is not good for patients."

BMJ Open is BMJ's first online general medical journal dedicated solely to publishing open access research.

Niall Dickson, chief executive of the GMC, said he welcomes the research, describing it as "a valuable contribution to an important and difficult issue which we take seriously and are actively addressing".

He added: "The number of complaints about doctors and other health professionals continues to rise and anyone who is subject to an investigation is bound to find it stressful, especially if the national regulator is involved.

"But, of course, our purpose is to protect patients and when serious allegations are made, we do need to investigate to establish if there is a case to answer.

"At the same time, we have a duty of care to these doctors. That is why we are doing more than ever to reduce the stress of our investigations, by offering support and doing everything we can to reduce the time doctors are in our processes."

Some 28 doctors committed suicide while under investigation over their fitness to practise between 2005 and 2013, according to a report commissioned by the GMC that was released last month.

It found that many of the doctors who killed themselves or died in suspected suicides had been suffering from mental health problems or had drug or alcohol addictions, and in some cases were under stress because of marriage breakdown, financial hardship and investigations by police.